DIAGNOSIS: Dust, fingerprints, or moisture on the small, recessed lens is blurring your picture.
FIX: You need the right tools and a gentle touch. 1) Unplug the camera first. 2) Use a can of compressed air (like for keyboards) to blow any loose dust out of the lens recess. 3) For smudges, use a microfiber cloth (the kind for eyeglasses or camera lenses) folded into a point. Gently wipe the lens in a circular motion. No liquids are needed for dust and fingerprints.
IF THAT DIDN'T WORK: If there's a stubborn spot, you can slightly dampen the corner of the microfiber cloth with distilled water. Wring it out completely so it's just barely damp. Gently wipe the lens and then immediately dry it with the dry part of the cloth.
HEADS UP: Never use window cleaner, isopropyl alcohol, or any harsh chemicals on the lens. They can damage the anti-reflective coating and plastic housing. Also, avoid using paper towels or tissues, as they can scratch the plastic lens.